Why do PDF files get corrupted?
PDF corruption happens more often than most people expect. Common causes: interrupted downloads (browser crash or network drop mid-transfer), storage device failure, email attachment encoding errors, incomplete saves when an application crashed, and file system errors after an improper shutdown. The result: a PDF that Adobe Reader, Chrome, or any viewer refuses to open.
How to repair a corrupted PDF free online — step by step
- Open ihatepdf.cv/repair-pdf in your browser — no sign-up required
- Drag and drop the damaged PDF onto the upload area
- Click Scan & Repair PDF
- Watch the forensic analysis and repair log in real time
- If recovery succeeds, click Download Repaired PDF — no watermark
The entire process runs locally in your browser. Your file is never uploaded anywhere.
The 5 repair strategies — explained
- Strategy 1 — Direct structural repair: Loads the PDF through pdf-lib's error-tolerant parser and immediately re-saves. Fixes many minor corruption issues.
- Strategy 2 — Stream length normalization: Scans every content stream, measures actual byte length, and corrects declared lengths that don't match.
- Strategy 3 — Manual xref reconstruction: Scans the raw binary for every object definition, builds a brand-new cross-reference table from scratch.
- Strategy 4 — Truncation recovery: Strips everything after the last valid endobj marker, then rebuilds the xref from surviving object data.
- Strategy 5 — Page-by-page salvage: Attempts to copy each page individually into a new document, skipping pages that throw errors.
After repair — stabilize the file
After a successful repair, consider using Flatten PDF to merge all page content into a clean static structure, which prevents future corruption from interactive layer issues. Then run Compress PDF to optimize the file size of the repaired document.
Frequently asked questions
What if all 5 strategies fail?
The file either was never a valid PDF, suffered catastrophic storage failure with no recoverable PDF objects, or was a zero-byte fragment. Contact whoever sent the file to request a fresh copy, or check cloud storage version history (Google Drive, Dropbox, OneDrive all keep file versions).
Is there a file size limit?
No server limit — the constraint is your device memory. Files up to 150MB work reliably on most desktop browsers.
Does the repaired file have a watermark?
No. ihatepdf never adds watermarks to any output file.